Outskirts of Distant Galaxies In Absorption

TL;DR

This paper reviews how quasar absorption spectroscopy reveals the properties of neutral and ionized gas in the outskirts of distant galaxies, enhancing understanding of baryon cycles over cosmic time.

Contribution

It provides a comprehensive review of empirical findings on neutral and ionized gas around distant galaxies using absorption-line studies, highlighting recent advances.

Findings

Constraints on star formation and chemical enrichment in galaxy outskirts

Insights into the distribution of neutral gas from DLA studies

Limited but informative data on ionized circumgalactic gas

Abstract

QSO absorption spectroscopy provides a sensitive probe of both the neutral medium and diffuse ionized gas in the distant Universe. It extends 21cm maps of gaseous structures around low-redshift galaxies both to lower gas column densities and to higher redshifts. Combining galaxy surveys with absorption-line observations of gas around galaxies enables comprehensive studies of baryon cycles in galaxy outskirts over cosmic time. This Chapter presents a review of the empirical understanding of the cosmic neutral gas reservoir from studies of damped Lya absorbers (DLAs). It describes the constraints on the star formation relation and chemical enrichment history in the outskirts of distant galaxies from DLA studies. A brief discussion of available constraints on the ionized circumgalactic gas from studies of lower column density Lya absorbers and associated ionic absorption transitions is presented at the end.